Building block



FIG. 1 is a perspective view of a building block showing my design.

FIG. 2 is a front elevational view thereof.

FIG. 3 is a rear elevational view thereof.

FIG. 4 is a left side elevational view thereof.

FIG. 5 is a right side elevational view thereof.

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a bottom plan view thereof.

The broken lines are for the purpose of illustrating portions of the article that form no part of the claimed design. 

CLAIM The ornamental design for a building block, as shown and described. 